The present invention relates to the art of applying plastic foams to a substrate and, more particularly, to apparatus providing improved control of the vertical profile of the applied plastic foam.
The invention finds particular utility in connection with the application of plastic foams to a roof deck and, accordingly, will be disclosed and described in detail herein in connection with such use. At the same time, however, it will be appreciated that the invention is applicable to the applying of plastic substrates other than roofing decks.
The spray application of plastic foams, such as polyurethane foams, to an underlying substrate is well known as shown, for example, in U.S. Pat. No. 4,209,557 to Edwards and U.S. Pat. No. 4,333,973 to Bellafiore, et al. In the Edwards and Bellafiore, et al. patents, a dispenser in the form of a spray nozzle is supported above a substrate for spraying an expandable plastic foam material downwardly thereunto. The nozzle and substrate are relatively displaceable in a given direction, and the nozzle is displaceable relative to the substrate along the path transverse to the given direction. More particularly, in Edwards the spray nozzle is slidably mounted on a fixed support extending transverse to the direction of movement of a sheet material substrate therebeneath, and the nozzle is reciprocated in opposite directions along the support to spray foam material on the sheet moving therebeneath. In Bellafiore, et al., the nozzle is mounted on a wheeled frame which is displaceable along an underlying substrate such as a roof deck, and the nozzle is mounted on the frame for movement therewith and for reciprocating displacement relative thereto along a path transverse to the direction of movement of the frame, whereby the foam material is sprayed downwardly onto the roof deck as the frame moves therealong. In both Edwards and Bellafiore, et al., and as is well known in connection with the spray application of plastic foams, the foam comprises liquid chemicals which are preheated and pumped through lengths of heated hose and are mixed in a mixer or spray gun and sprayed onto the underlying substrate where they cure in a matter of seconds.
In connection with the spraying of plastic foam material onto a roof deck as shown in Bellafiore, et al., and as recognized in Edwards, the reciprocation of the spray nozzle in opposite directions requires the latter to decelerate, stop and reaccelerate in the opposite direction at each end of the path of movement thereof, whereby there is a vertical buildup of the plastic foam along the opposite edges of a layer of plastic foam applied to the underlying substrate. In Edwards, this problem is addressed by mounting the nozzle for the vertical plane of the spray to be at an angle with respect to the direction of reciprocation of the nozzle as it moves from one end of the path to the other, and to pivot the nozzle about a vertical axis at each of the opposite ends of the path of reciprocation, whereby the plane of the spray is shifted about the vertical axis so as to be at an angle in the opposite direction relative to the path of reciprocation as the nozzle moves back toward the first end of the path. While such pivotal displacement of the nozzle may preclude a vertical buildup of plastic foam along the edges of a sprayed layer, the shifting of the nozzle about a vertical axis at the opposite ends of the path of reciprocation results in a herring bone-like pattern along the opposite edges. In certain applications, such as the applying of foamed plastic on a roof deck, several laterally adjacent runs are required in which the adjacent edges of the applied foam overlap, and such a herring bone-like pattern would not enable obtaining a smooth transition between the adjacent passes. While Edwards suggests his spray nozzle could be pivotal about a horizontal axis, such mounting in accordance with his disclosure would provide for the plane of the spray to be inclined in one direction relative to vertical during reciprocation of the nozzle to one end of the path thereof and then reversed in connection with reversal of the direction of movement of the nozzle toward the first end of the path. The reversal of the incline of the nozzle necessarily moves the outlet end thereof closer to the substrate than it was during the approach to the end of the path, and this would either provide for an overlay of the material at the turning point and/or gouging of the material beneath the nozzle as the material would not have had time to set or cure. Again, in connection with certain applications of foamed plastic material to a substrate, such as the laying of adjacent passes of foamed plastic on a roof deck, such overlaying or gouging would preclude obtaining the desired smooth transition between the adjacent passes.